Background: High body temperature in the first 12-24 h after stroke onset is associated with poor functional outcome. The Paracetamol (Acetaminophen) In Stroke (PAIS) trial aimed to assess whether early treatment with paracetamol improves functional outcome in patients with acute stroke by reducing body temperature and preventing fever. Methods: In a multicentre, randomised, double-blind, placebo-controlled trial, patients with ischaemic stroke or intracerebral haemorrhage and body temperature between 36°C and 39°C were randomly assigned treatment with paracetamol (6 g daily) or placebo within 12 h from symptom onset. Treatment allocation was based on a computer-generated list of random numbers with varying block size. The primary outcome was improvement beyond expectation on the modified Rankin scale at 3 months, according to the sliding dichotomy approach. This trial is registered, number ISRCTN74418480. Findings: Between March, 2003, and May, 2008, 1400 patients were randomly allocated treatment. 260 (37%) of 697 patients receiving paracetamol and 232 (33%) of 703 receiving placebo improved beyond expectation (adjusted odds ratio [OR] 1·20, 95% CI 0·96-1·50). In a post-hoc analysis of patients with baseline body temperature 37-39°C, treatment with paracetamol was associated with improved outcome (1·43, 1·02-1·97). There were 55 serious adverse events in the paracetamol group (8%) and 70 in the placebo group (10%). Interpretation: These results do not support routine use of high-dose paracetamol in patients with acute stroke. Paracetamol might have a beneficial effect on functional outcome in patients admitted with a body temperature 37-39°C, but this post-hoc finding needs further study. Funding: Netherlands Heart Foundation.